A group of angel investors including SecondMarket founder Barry Silbert has invested $510,000 in BitPay, a firm that processes payments for merchants in the digital currency Bitcoin. BitPay says it plans to use the new capital to move its headquarters to Atlanta from Orlando and to hire up to five new employees. BitPay was self-funded during its startup phase and currently has two full-time employees, founders Anthony Gallippi and Stephen Pair. Founded in 2011, BitPay lets businesses accept payments using Bitcoin, a decentralized, unregulated online currency that is an increasingly popular — and controversial — means of doing business online. BitPay says its transaction volume has grown rapidly since its founding, with over $3 million processed in 2012. The pace picked up after it signed WordPress , the blog publishing platform, as a customer. "WordPress lit a fire, and we...